fix(db9): bump to 0.2.1 to pull @sandbank.dev/core@^0.3.6

Older @sandbank.dev/core versions (0.1.1–0.3.5) were published with
an unresolved "workspace:*" in peerDependencies, which npm can't parse.
db9@0.2.0 resolved core to ^0.2.0 → 0.2.1, tripping the bug.
Upgrading the constraint routes consumers to the fixed core 0.3.6+.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: guo-yu

packages/db9/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@sandbank.dev/db9",
-  "version": "0.2.0",
+  "version": "0.2.1",
   "description": "db9.ai service adapter for Sandbank — serverless PostgreSQL for AI agents",
   "license": "MIT",
   "type": "module",